Originally Posted by
truckjohn
DW, I sort of arrived at the same place as you did wrt the edge "falling off" of chisels. AKA chipping or rolling rather than actually "dulling".
And I suppose it sounds dumb to say out loud but that's the first hurdle, right? Get the edges prepped so they don't chip or roll and then go from there.
I think this is probably one place where hand sharpening excels jigs. The natural motion of the hands and arms means you get a teeny little rounding of the edge - and that makes it cut a LOT longer. I found this quite pronounced with chisel backs.... A chisel back lapped carefully flat out to the very edge has a much shorter life than one which is just barely perceptibly rounded from a few passes on a strop. It's not enough where it goes squirrely in a cut or won't register properly, but you can just barely watch the light follow a slightly rounded path at the tip on a reflection.
I did some experiments increasing the edge angle with fully jigged sharpening and it took a lot more angle to eliminate the rolling/chipping.... Like way over 40-degrees in a lot of cases. Cutting effort also greatly increased. I didn't like it.
I have a feeling this has a LOT to do with the effect of blade thickness behind the edge on perceived cutting force. This is where Microbevels seem to excel unless the Microbevel isn't micro. ;).
So for example - a 20-degree sharpened chisel with a machine polished edge may be at nearly 50-degrees for the first 0.0005" - but the steel is thinner 0.010" back where the chip hits so it feels sharper than a jig sharpened 35-degree bevel.
That's probably why Paul Sellers' hard stropping makes edges last longer.... It slightly rounds the very very tip and the edges are less likely to roll or chip out....
As an aside - I think that thickness also makes a difference in the perceived feel of a chisel working on an older hex-bolster bench chisel vs a new plastic handle butt chisel. The old chisel is perhaps half the thickness at the working end.... Thus it "feels" sharper even though mechanically the edge is prepped the same...